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  • Battery, generator or combo?

    I am getting ready to build a new home and am starting to plan out a solar plan for it. The one place I am getting stuck is backup power. I do not expect frequent power outages, but want the piece of mind that at least parts of the home will always have power. If I did not have solar then it would be simple, purchase a NG generator, and add a few UPS on things that I don't want to power off while the generator spins up, but now that I want solar it makes it a bit more complicated.

    I am looking at a 30-35 kw grid-tied solar system, During a power outage I would like to have at least 10 KW available during a 6 hour power outage. I like the idea that most of the critical loads would not notice the outage with batteries. I also like the idea that the NG generator could keep the power going if I have an outage that last for days. In my current home I had a power outage that lasted 3 days due to an ice storm. Very rare to last that long but just knowing I have that backup is nice. Normally there may be 1 or 2 outages a year lasting 1-6 hours.

    With that said, I would love to hear the thoughts of everyone. In all cases, I will still put in solar, but which path would you follow? Generator only? Batteries only? or a combo?

    If the batteries are only used for rare cases does that matter on the life of the batteries? Do you still need to drain them some on a regular basis? How often would those batteries need to be replaced using todays technology?

    Here are my pro/con list so far:

    Batteries Pro:smooth transition, little maintenance, tax savings on purchase with solar system. Con:Needs to be replaced, limited amount of power.

    Generator Pro: could supply power for days, longer life then batteries. Con: Fuel is expensive, requires maintenance

    Are there any advantages to one of those choices over another?

    Thanks for any information you may share!

  • #2
    Originally posted by Cyclops View Post
    I do not expect frequent power outages, but want the piece of mind that at least parts of the home will always have power. If I did not have solar then it would be simple, purchase a NG generator, and add a few UPS on things that I don't want to power off while the generator spins up.
    What I have done, and recommend, is use your original non solar
    backup plan. PV solar is a terrible backup, and significant energy
    runs into a lot of expense over that simple generator. Bruce Roe

    Comment


    • #3
      If you can get something like a tesla powerwall, than that will meet your goal. It will be expensive and something like a generac would be much more practical and be able to run a lot more. Some have even claimed to charge the powerwall early and use the electricity at times in the day where its more expensive and get some savings that way.

      When I see 30-35 kw system, that is pretty big. I decided against solar for the house, but commercial systems in my area started after 10 kw - 15 kw.

      Comment


      • #4
        Originally posted by Cyclops View Post
        I do not expect frequent power outages, but want the piece of mind that at least parts of the home will always have power.
        +1 bcroe

        Okay, but that that "piece(sic) of mind" you wish for will not come cheap or without recurring costs. I myself would not even put in a NG generator if the area is not known for frequent or lengthy power outages. A small portable gasoline generator and an extension cord will do all I truly need to get by in an outage. Others have different needs of course but why all the cost and effort to install backup power when it doesn't even sound like you have any significant issue with outages?


        Dave W. Gilbert AZ
        6.63kW grid-tie owner

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        • #5
          My lifetime experiences (65 years) of power outages of longer than 4 hours in Northern Illinois is a grand total of ONE!!! I have a gasoline generator if it goes longer, so I just have a grid tied system. Batteries are just an added cost with no benefit. Whether you use the batteries often or they just "standby" for peace of mind you should replace them every 10 years at the max.

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          • #6
            Thanks everyone. I think you are winning me over to stick just with a generator for backup power. I too am in IL but the southern part The 30kw would cover all of my usage, I too was a little surprised when I calculated what size system I will need, but luckily we are building on 10 acres worth of farm land and have the space for a nice ground mount system. What I has been thinking is I could get a combo system after seeing a few battery systems in the $1500 range and with thousands of cycles to it's life. With the number of basic UPS's I would need could easily cost $1500 every 5 years then the batteries tied to solar could maybe become a savings pull allow for the panels to still operate during the day without needing to run a generator.

            Comment


            • #7
              For a ground mount in IL, review my sticky on making snow much
              less of an issue. Bruce Roe

              Comment


              • #8
                We have a 7KW solar system installed in northern California and power outages are becoming more common in our part of town. We have outages lasting 3-5 hours every couple on months and yesterday it lasted 18 hours. Wondering if we should get a Tesla Powerwall or a Generac 18KW generator. We have been quoted ~$12K for the 10KW Powerwall and $25K for a generator. It's another surprise that Generac site says generator price starting at $4939 (Transfer Switch, Installation, Taxes and Shipping Not Included) but the installed quote is about 5 times the MSRP.
                What factors should we consider in choosing one of these options?

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                • #9
                  Originally posted by rmk9785e View Post
                  We have a 7KW solar system installed in northern California and power outages are becoming more common in our part of town. We have outages lasting 3-5 hours every couple on months and yesterday it lasted 18 hours. Wondering if we should get a Tesla Powerwall or a Generac 18KW generator. We have been quoted ~$12K for the 10KW Powerwall and $25K for a generator. It's another surprise that Generac site says generator price starting at $4939 (Transfer Switch, Installation, Taxes and Shipping Not Included) but the installed quote is about 5 times the MSRP.
                  What factors should we consider in choosing one of these options?
                  A 10kwh battery will not last you very long. I'd get the battery & the generator. I recall the smokey days a few years ago, no sun for 3 days, just a dull red glow. No solar to charge batteries
                  Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
                  || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
                  || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

                  solar: http://tinyurl.com/LMR-Solar
                  gen: http://tinyurl.com/LMR-Lister

                  Comment


                  • #10
                    Originally posted by rmk9785e View Post
                    We have a 7KW solar system installed in northern California and power outages are becoming more common in our part of town.......
                    What factors should we consider in choosing one of these options?
                    If you are in Northern California a Tesla Powerwall can leverage your existing solar to save you money by not having to pay peak rates for Energy. A generator can not do that.
                    9 kW solar. Driving EVs since 2012

                    Comment


                    • #11
                      Originally posted by Ampster View Post

                      If you are in Northern California a Tesla Powerwall can leverage your existing solar to save you money by not having to pay peak rates for Energy. A generator can not do that.
                      Why not ? Fire it up and get power at will.

                      Besides, as Mike 90250 notes, sun may not be available to charge a battery. Besides, As a backup, reliability matters more than being trendy.

                      Given the cost of batteries just now, and their reliance on what may be an unreliable, or at least less reliable source of energy, I'd skip the storage as the darling of treehuggers who seem to have little financial savvy in such matters and get a propane fired generator for backup, but only after I had a serious plan to learn to and live like an off gridder during outages of unknown length.

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